Macraes Gold Mine

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Macraes Gold Mine, Otago, New Zealand, (NASA satellite photo) as of Dec 2008

The Macraes Gold Mine is New Zealand's largest gold mine with an expected gold production of 195,000 ounces of gold in 2008.

geography

The Macraes gold mine is located directly on the settlement Macrae's Flat , a historic site in Otago , left over from the days of the gold rush in Otago . The mine is located about 55 km north of Dunedin in the Waitaki District and thus on the South Island of New Zealand . The Taieri Ridge adjoins to the north and west, the valley runs along the Shag Rivers to the east and a gently sloping mountain landscape up to 700  m high extends to the south .

geology

Embedded in layers of mica schist , which, with the exception of the area around Marlborough , can be found east along the Alpine Fault and spread throughout Otago in the Mesozoic , is the geologically interesting Hyde-Macraes Shear Zone on the Hyde-Macraes Flat line . This northwest running offset of the rock layers is approx. 30 km long, has a width between 5 m and 130 m and slopes gently at 15 degrees in a northeast direction towards the valley of the Shag River. In the Mesozoic Era, liquid material was pressed upwards under high pressure and led to the formation of this fracture and the shifting of the layers. It is assumed that at temperatures between 300 and 400 ° C, parts of the liquid material mineralized to form gold and scheelite, and so the 5 to 10 cm wide and up to 20 m long gold veins were formed.

history

Frasers Pit , one of the Macraes Gold Mine open pit pits .

The very young history of the gold mine began in 1983. Although gold was found in the area around Macraes Flat in 1862 and led to a gold rush here after a two-year delay , the prospecting for gold was discontinued in the 1940s due to inefficiency. With the techniques available at that time, the suspected gold could no longer be mined economically.

With the global rise in the price of gold in the late 1970s, the New Zealand government launched a nationwide exploration program in the early 1980s that included finding high-yield gold deposits in Otago. In 1983 the first geological investigations began in the Macraes field. Newly developed mining methods promised to be able to economically mine the estimated gold deposits within 10 years. In 1990 the Macraes Mining Company Ltd. founded for this project began . (MMCL) with the gold mining in the open pit .

The enormous need for money combined with the prospect of a lucrative business led to the takeover of Macraes Mining Company Ltd. in 1998 . by Union Gold Mining Company NL (UGM), founded in Australia in 1986 , which renamed Gold and Resource Developments NL (GRD) in the same year . The Macraes Mining Company Ltd. , which was run as a branch of Gold and Resource Developments NL from December 1998 , took over the name of the Australian-born company in May 1999 and operated under Gold and Resource Developments (NZ) Ltd. for only 14 months . to join GRD Macraes Ltd. in July 2000 . to be renamed. In December 2003 the company OceanaGold Corporation was founded in Australia , which from now on owned the mining rights of the Macraes Gold Mine . In May 2006, GRD Ltd. sold their majority stake in OceanaGold and thus gave up their majority stake.

In 2004, after more than 1.8 million ounces of gold had been mined since 1990, the further gold deposits in the Macraes Gold Mine were estimated at 3.9 million ounces, with a concentration of 1.4 grams of gold per ton Rock.

today

The Macraes Gold Mine is considered the largest gold mine in the country. In addition to numerous open-cast mines, an ore processing plant, an oxidation plant , mud ponds and, since 2006, an underground pit (Fraser's Underground) are operated on the mine site .

According to the company's annual report, the opencast mines produced over 2.5 million ounces of gold up to 2007 and thus represented the economic basis of the company. The ore processing plant, in which gold-bearing ore is separated from waste rock , achieved its previous maximum output in 2007 with an annual throughput of 5,564,873 tons. The first underground construction of the Macraes Mine is to develop gold veins at a depth of only 8.9 meters, which promise 2.1 grams of gold per ton of rock. It is said to be the least deep underground mine in the world. In the oxidation plant, the gold is extracted from the ore using the cyanide leaching process . In order to be able to operate the process of gold extraction from the ore more economically, the gold ore from the gold mine near Reefton is brought to Macraes for processing by rail across the New Zealand Alps .

The estimated and proven gold occurrences in the Hyde-Macraes fault are substantial. The existence of the gold mine also depends on the gold price, the efficiency of the mining methods and the renaturation costs. OceanaGold promises the existence of the gold mine for at least six years, with a gold yield of around 200,000 ounces per year. The mine’s recoverable gold deposits are expected to last for up to 35 years.

literature

  • Simon Cox, Dave Craw, Field Trip Guides - East Otago Gold - Annual Conference , Geological Society of New Zealand Inc, 2003, ISBN 0-908678-97-5
  • MJ Begbie, D. Craw, Geometry and petrography of stockwork vein swarms, Macraes mine, Otago Schist, New Zealand , New Zealand Journal of Geology & Geophysics, Vol. 49, p63-73, 2006.
  • Colin N. Windsor, The relationship between the Hyde-Macraes Shear Zone, deformation episodes, and gold mineralization potential in eastern Otago, New Zealand , New Zealand Journal of Geology and Geophysics, Vol. 34, 1991.
  • Explore New Zealand Gold , Crown Minerals, Ministry of Economic Development, Wellington, 2004, ISBN 0-478-26331-7
  • OceanaGold Corporation Annual Report 2007 , OceanaGold Corporation, Melbourne, Victoria, Australia, 2007.

Web links

Individual evidence

  1. ↑ CEO Steve Orr, Denver Gold Conference, September 2008
  2. ^ Macraes Flat . New Zealand South , archived from the original on January 13, 2015 ; accessed on January 17, 2016 (English, original website no longer available).
  3. ^ Macraes gold mine, East Otago, New Zealand . Department of Geology, University of Otago , accessed January 17, 2016 .
  4. ^ Oceana Gold Risk in New Zealand. Goldinvest Media GmbH, February 10, 2005, archived from the original on August 28, 2014 ; accessed on April 29, 2019 (English, original website no longer available).
  5. ^ OceanaGold Corporation Annual Report 2007 , OceanaGold Corporation, Melbourne, Victoria, Australia, 2007.
  6. ↑ Macraes Mine - www.showcaves.com by Jochen Duckeck

Coordinates: 45 ° 22 ′ 16 ″  S , 170 ° 27 ′ 13 ″  E